i feel like a sku-morphic windows 9 with the windowed rt apps + start menu with live tiles was the end goal all along. by releasing windows 8 they were able to:
1) buy more time
2) get real feedback/testing for the rt/tablet side of things. despite being forced, it exposed a lot of people to the idea of a usable windows tablet
3) use a throwaway os to get past the 'every other major version of windows is crap' belief (i don't believe this, but the perception is out there)
i suspect windows 9 will be released alongside a more complete rt api that will allow easy porting from win32, at least for the apis used heavily in enterprise.